Under the laws of thermodynamics, the total energy consumed to perform any work can be generally defined as exergy (the energy, which is available to perform the actual work) and anergy (wasted and effectively has no capacity to perform work). The exergy of a system is the maximum useful work possible during a process that brings the system into equilibrium with a heat reservoir. Exergy is the energy that is available to be used. After the system and the surroundings reach equilibrium, the exergy is zero. An example of such energy is automobile exhaust heat that is ejected to the atmosphere. Energy is neither created nor destroyed during a process, it simply changes from one form to another. In contrast, exergy is always destroyed when a process is irreversible. This destruction is proportional to the entropy increase of the system together with its surroundings. The destroyed exergy has been called anergy. If this anergy is captured and is used to perform other useful work, the exergy efficiency of the system will improve significantly.
However, this capture and use of anergy is still inefficient. The American economy wastes 86% of all the energy used per year in the production of goods and services. One can easily imagine that waste of this magnitude creates an array of costs that weakens the nation's economic and social well-being. If this exergy can be improved even from about 14% to about 20%, it could lead to a $2.3 trillion addition to the economy. One type of waste is food loss. The overall food loss in the United States is estimated to be $161.6 billion and nearly 40% of it comes from improper handling, storage, and transportation problems.
Attempts have been made to alleviate current issues with refrigeration transportation systems. Examples include U.S. Pat. No. 8,881,539; EP149527B1, EP1495271, EP1688685A1, JP162104A2, US20077201017, US200690197053A1, WO06084262A1, US20070019708A1, WO06094304A3, WO06110944A1, WO06137930A3, US20050126211A1, US20077171824, and EP0836060B1. However, none are sufficiently effective.
U.S. Pat. No. 6,374,630 for “Carbon dioxide absorption heat pump” to Jones discloses a traditional absorption cycle utilizing supercritical carbon dioxide. The '630 patent does not teach an absorber having either a very low vapor pressure, a boiling point less than 50° C., or any means to achieve a coefficient of performance better than 0.70. The '630 patent further does not teach any nonthermal means to reduce desorption temperature, nor the extraction of expansion energy.
United States Patent Application No. US 2003/0182946 for “Method and apparatus for using magnetic fields for enhancing heat pump and refrigeration equipment performance” to Sami et al. utilizes a magnetic field that is operable to disrupt intermolecular forces and weaken intermolecular attraction to enhance expansion of the working fluid to the vapor phase. Magnetic field energy has been found to alter the polarity of refrigerant molecules and disrupt intermolecular Van der Waals dispersion forces between refrigerant molecules, though Sami et al. does not teach the utilization of a magnetic field to reduce desorption energy.
United States Patent Application No. US 2002/0078696 for “Hybrid heat pump” and U.S. Pat. No. 6,539,728 for “Hybrid heat pump,” both to Korin, disclose a hybrid heat pump system that includes (i) a membrane permeator having a permselective membrane capable of selectively removing vapor from a vapor-containing gas to yield a dry gas, and (ii) a heat pump having (a) an internal side for exchanging thermal energy with a process fluid, (b) an external side for exchanging thermal energy with an external environment, and (c) a thermodynamic mechanism for pumping thermal energy between the internal side and the external side in either direction. Korin uses membranes to pre-condition air in conjunction with a refrigeration air conditioning system, and does not perform or teach any phase separation within the refrigerant itself. Furthermore, although membranes have been used in various separation applications, their use for heat pump systems has been limited.
U.S. Pat. Nos. 4,152,901 and 5,873,260 propose to improve an absorption heat pump by using of a semipermeable membrane and pervaporation membrane, respectively. U.S. Pat. No. 4,467,621 proposes to improve vacuum refrigeration by using sintered metal porous membrane, and U.S. Pat. No. 5,946,931 describes a cooling evaporative apparatus using a microporous PTFE membrane. These patents do not teach the use of membranes for phase separation within an absorption system, but rather within adsorption systems.
U.S. Pat. No. 4,152,901 to Munters discloses a method and apparatus for transferring energy in an absorption heating and cooling system where the absorbent is separated from the working medium by diffusing the mixture under pressure through a semi-permeable membrane defining a zone of relatively high pressure and a zone of relatively low pressure, higher than the ambient pressure.
U.S. Pat. No. 5,873,260 for “Refrigeration apparatus and method” to Linhardt, et al. utilizes the increased pressure of the absorbent/refrigerant solution that is then supplied to a pervaporation membrane separator to provide as one output stream a vapor-rich refrigerant, and as another output stream a concentrated liquid absorbent. The '260 patent does not teach supercritical fluids.
U.S. Pat. No. 6,918,254 for “Superheater capillary two-phase thermodynamic power conversion cycle system” to Baker discloses a two-phase thermodynamic power system including a capillary device, vapor accumulator, superheater, an inline turbine, a condenser, a liquid pump and a liquid preheater for generating output power as a generator through the generation of a staggered or pulsed release of vapor flow. The capillary device, such as a loop heat pipe or a capillary pumped loop, is coupled to a vapor accumulator, superheater, the inline turbine for generating output power for power generation, liquid pump and liquid preheater. The capillary device receives input heat that is used to change phase of liquid received from the liquid preheater, liquid pump and condenser into vapor for extra heating in the superheater used to then drive the turbine. A superheater in combination with a liquid pump and preheater are implemented for use with the evaporator for improved thermal efficiency while operating at maximum cycle temperatures well below other available power conversion cycles.
U.S. Pat. No. 5,899,067 for “Hydraulic engine powered by introduction and removal of heat from a working fluid” to Hageman discloses a thermal source as a means to increase a working fluid's pressure which in turn drives a piston for pumping, or alternatively refers to the piston being connected to a generator to result in electricity.
International Patent Application No. WO2007082103 to Gurin discloses a safe, environmentally friendly absorptive cooling, heating, and energy generation process is provided. Gurin uses a carbon dioxide absorption cycle that utilizes a liquid, non-toxic absorbent such as ionic liquids, from which the carbon dioxide gas is absorbed. Only the carbon dioxide refrigerant is circulated to the evaporator and condenser heat exchangers, the components directly in contact with breathable air. The further incorporation of a thermodynamic hydraulic pump increases the energy efficiency, especially in combustion power generation cycles, as it eliminates a substantial portion of energy utilized for compression prior to combustion.
U.S. Pat. No. 4,031,712 to Costello discloses one or two compressors added to a conventional absorption-refrigeration system. The compressor may be added so as to provide for compressing the vapor refrigerant from the evaporator of the refrigeration system before introducing it into the absorber or a compressor may be added so as to provide for compressing the vapor refrigerant from the generator of the refrigeration system before introducing it into the condenser. The preferred modification includes compressors added at both points. The Costello system permits a balance between the amount of energy supplied thermally from the solar collector and the amount of energy supplied by electricity to compress the refrigerant vapor.
Another approach to solar energy powered cooling has been the co-called Rankine-cycle solar air conditioner. A Rankine cycle refers to the successive compression, heating, expansion, and condensation of a working fluid in a heat engine, such as a steam engine. The cycle may either be closed, where the working fluid is recycled, or open, where the expanded and condensing steam is simply vented to the air. In the Rankine cycle solar air conditioner, solar heated hot water at 215° F. (102° C.) from solar panels enters a multiple stage boiler where a working fluid of a liquid refrigerant, R-113 (trichlorotrifluoroethane) is vaporized and used to turn a small turbine. The expanded refrigerant is cooled, condensed and pump returned to the boiler. The turbine is used to drive a compressor in a conventional vapor compression refrigeration system.
In a conventional vapor compression refrigeration system, a refrigerant, which is a compressible, condensable gas, is compressed in a compressor, passed to a condenser where the gas is condensed to a liquid, and passed through an expansion device to a low-pressure evaporator, where evaporation and cooling take place. The compressor in the Rankine cycle solar vapor compression system is driven either by the turbine or by a back-up electric motor.
U.S. Pat. No. 4,100,755 to Leonard describes an absorption refrigeration system suitably arranged for utilizing solar energy as a primary source of power to the system generator. Leonard describes the use of any other source of low temperature energy, such as normally unrecovered heat energy produced by many manufacturing processes or geothermal sources can be employed in a similar manner. Leonard also describes an absorption system employing water as a refrigerant and lithium bromide as an absorbtive solution.
U.S. Pat. No. 4,178,989 to Takeshita et al. describes a system to accomplish both air cooling and air heating of indoor space by utilizing solar energy. In principle the disclosed system is an absorption refrigeration system, wherein a solution of an evaporable refrigerant in a less evaporable solvent is passed through a solar collector-generator, but the system has additional fluid passages with the provision of changeover valves arranged so as to pass the refrigerant in heated and vaporized state from the collector-generator to an indoor heat exchanger, bypassing the condenser of the refrigerator, thereby to accomplish air heating and return the refrigerant in liquid state from the heat exchanger to the collector-generator, bypassing the absorber of the refrigerator.
In solar heating and cooling systems, development of high efficiency collectors to collect heat from solar radiation is one of main technological tasks, and reduction of heat loss during the transfer of heat from a solar collector to other components is another important task. From a practical viewpoint, it is also important that the use of a solar system affords a fuel saving large enough to pay back initial investments to the solar system in a satisfactorily short time. In this regard, it is quite desirable that a solar system can accomplish both air heating and air cooling because then the amount of fuel or money saving per year can be increased.
The use of solar energy for air cooling or air conditioning is made almost always by means of either a vapor compression refrigerator or an absorption refrigerator. In the former case, hot water (or an organic heating medium) supplied from a solar collector is used to generate a high-pressure vapor of a refrigerant such as Freon, with which a Rankine cycle engine of the refrigerator is operated. A solar system of this type can operate with high efficiency only if use is made of a highly efficient solar collector since the thermal efficiency of the compression refrigerator is unsatisfactory and below than that of an absorption refrigerator when the temperature of the heating medium does not exceed about 100° C. In the case of an absorption refrigerator system in which usually water and lithium bromide are employed respectively as refrigerant and absorber, hot water (or an organic heating medium) provided by a solar collector serves as the heat source for operation of the refrigerator. This type of solar cooling system too requires that the heating medium is heated to a considerably high temperature. It is possible to use this type of system also as a solar heating system, but the temperature requirement to the heating medium for heating operation is almost like that for cooling operation. Since it is difficult to realize such a high temperature in winter, an absorption refrigerator system is rarely practiced as a solar heating system.
U.S. Pat. No. 4,373,347 to Howell et al. describes a hybrid absorption system utilizing a low grade thermal energy source which includes means for contacting process air with a liquid desiccant solution, first cooling means placed within the contacting means in heat exchange relation with the process air; means for absorbing the heat transferred by the first cooling means, means for mixing water and strong liquid desiccant, second cooling means placed in heat exchange relation with the mixing means; concentrating means utilizing low grade thermal energy to concentrate the desiccant solution from the contacting means and the mixing means, and condensing means for condensing water vapor received from the concentrating means. Howell et al. discloses a contacting means with an open absorber and is employed in conjunction with an absorption-refrigeration system such that the system comprises an open absorber using a liquid desiccant solution to absorb moisture from air passing therethrough, a cooling coil as a first cooling means positioned within the open absorber for cooling air passing through the open absorber, an absorber as mixing means for absorbing water vapor into the strong liquid desiccant solution, a generator as concentrating means to concentrate the desiccant solution received from the open absorber and the absorber, a condenser as condensing means for vapor driven off in the generator and an evaporator as means for absorbing the heat transferred from the process air to the cooling coil, said evaporator adapted to vaporize the condensed vapor from the condenser and allow transfer of the resultant vapor to the absorber.
International Patent Application No. WO2007082103 to Gurin discloses a multistage absorption heat pump system, also known as a cascading system, whereby one distinct refrigerant A is used in at least one distinct stage and at least one other distinct refrigerant B is used in at least one other distinct stage. Each stage is in effect a distinct thermodynamic cycle, though each stage is coupled to the other as one's output is the other's input. The Gurin high efficiency absorption heat pump device leverages the differences in desorption temperature of a refrigerant A and absorption temperature of refrigerant B. Yet another configuration disclosed in Gurin is the high efficiency absorption heat pump device having direct infusion of a parallel energy generation system or combustor such that its exhaust is infused into the absorber, capturing latent energy from the exhaust stream. Another Gurin implementation utilizes techniques to selectively enable the refrigerant to enter the absorber, thus the exhaust air is treated to remove byproducts. This implementation achieves concurrent carbon dioxide sequestration. The cooling available from the high efficiency absorption heat pump device is then utilized to precool the combustion air to increase turbine capacity and energy efficiency.
As is well known, refrigeration systems generally comprise either (a) a vapor compressor that compresses a gaseous refrigerant such as a fluorinated hydrocarbon, a condenser to condense the vapor to liquid form, an expansion valve to reduce the pressure of the liquid, and an evaporator to cool the air or water by evaporation of the refrigerant; or (b) an absorber containing an absorbent such as a solution of lithium bromide and water that absorbs the gaseous refrigerant such as water vapor, a pump that raises the pressure of the solution after absorption of the vapor, a generator in which the solution is heated to drive the refrigerant vapor off at high pressure, a condenser in which the high-pressure vapor is cooled until it condenses into liquid form, and expansion valve by which the liquid is brought to a lower pressure, and an evaporator to cool the air or water by evaporation of the refrigerant.
The disadvantage of the vapor compression system described under (a) above is that large amounts of electric power are required to compress the vapor, so operating expenses are high and a valuable energy resource is consumed. The disadvantage of the absorption system described in (b) above is that high temperatures are required to drive the refrigerant out of the solution in the generator. In addition, a highly efficient coolant such as cold water is required in the condenser and the absorber. The high temperatures of the generator are attained usually by combustion of fossil fuels, so operating expenses are high and a valuable energy resource is consumed. To attain these high temperatures using a renewable energy source such as solar energy, large, costly, and inefficient collector systems are required.
Accordingly, what is needed is a vapor absorption refrigeration system that results in high exergy efficiency. However, in view of the art considered as a whole at the time the present application was made, it was not obvious to those of ordinary skill in the field of this disclosure how the shortcomings in the art could be overcome.
While certain aspects of conventional technologies have been discussed to facilitate disclosure of the instant application, Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed subject matter may encompass one or more of the conventional technical aspects discussed herein.
The present application may address one or more of the problems and deficiencies in the art discussed above. However, it is contemplated that the present application may prove useful in addressing other problems and deficiencies in a number of technical areas. Therefore, the claimed subject matter should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein.
In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.
In volumentric heating applications of microwave and radiofrequency electromagnetic radiations, permittivity can be related to chemical composition, physical structure, frequency, and temperature, with moisture content being the dominant factor. Dielectric properties (dielectric contant—ε′, dielectric loss factor—ε″) are primarily determined by their chemical composition (presence of mobile ions and permanent dipole moments associated with water and other molecules) and, to a much lesser extent, by their physical structure. Power dissipation is directly related to the dielectric loss factor ε″ and depends on the specific heat of the food, density of the material, and changes in moisture content (for example, vaporization).
Permittivity also depends on the frequency of the applied alternating electric field. Frequency contributes to the polarization of molecules such as water. In general, dielectric constant increases with temperature, whereas loss factor may either increase or decrease depending on the operating frequency. The heating uniformity and temperature elevation rate depends dielectric properties and thus differential volumentric heating can be achieved in mixtures.